Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Phase shift by less than period of input
Reexamination Certificate
2000-08-22
2002-05-07
Wells, Kenneth B. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Phase shift by less than period of input
C327S131000, C327S134000
Reexamination Certificate
active
06384653
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to control of a CMOS phase interpolator.
BACKGROUND OF THE INVENTION
Accurate control of a zero crossing point of a signal has several useful applications, including phase interpolation for a varying signal. What is needed is a phase interpolation system in which the zero crossing point varies linearly with a controllable parameter that can be varied over a finite parameter range. Preferably, the range of the zero crossing parameter should be flexible so that the range can be increased or decreased according to the particular circumstances.
SUMMARY OF THE INVENTION
These needs are met by the invention, which provides a CMOS phase interpolator in which a linear change in a parameter in the input control signal produces a linear change in phase of the output waveform relative to the input waveform. The interpolation approach works on a principle of weighted addition of two two-sided triangle waves that have a selected phase difference. The weighted sum of two triangle waves produces an output signal having a zero crossing point that ranges over the selected phase difference. Each of two spaced apart segments within the period of the triangular waves provides a zero crossing point, and the location and temporal length of each segment can be varied by choice of a relative phase of the two triangular waves.
REFERENCES:
patent: 4962344 (1990-10-01), Bohrer
patent: 5367212 (1994-11-01), Rabii
patent: 5717350 (1998-02-01), Bohrer
Cadence Design Systems
Schipper John F.
Wells Kenneth B.
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